Leakage of fuel gas from pipelines is a serious problem. In U.S. Pat. No. 4,304,805 there is described a process for sealing leaks in buried gas pipes by polymerization of volatilized amino-silane monomers. This same reference discusses other prior art methods for sealing gas pipes and includes the following statement:
In U.S. Pat. No. 3,507,725 to Hylak et al., there is disclosed a method of repairing gas main fibrous packed joints with a liquid sealing material which may be a liquid monomer such as styrene monomer, by introducing the monomer into the gas main in liquid form, and permitting it to flow to a low point in the system where a leaking joint exists, the packing of which becomes saturated with the sealant which then polymerizes over a relatively long period of time, namely six weeks to three months. Styrene is employed as a liquid, and no specific catalyst is named in the patent. PA1 (a) long chain acrylic ester: 20-80% PA1 (b) hydroxy functional acrylic ester: 15-50% PA1 (c) acid monomer: 0.5-5% PA1 (d) plasticizer: 5-30% PA1 (e) polyfunctional acrylic ester: 0.1-5%
Recently there has been developed an apparatus for sealing gas pipe leaks which includes means for moving the apparatus through a pipeline to a leak site, inflatable elongated balloon or bladder means having three separate adjacent inflatable chambers, means for selectively inflating and deflating the respective chambers, and means for injecting a curable sealant fluid between the center balloon chamber and the inner pipe wall. The apparatus is operated so as to position the central balloon chamber at a leak, inflate the two outer balloon chambers so as to enclose a central leak containing area within the pipe, inject the curable sealant into the enclosed area and then inflate the central balloon chamber to move the fluid into the porosities causing the leak where the fluid is cured. The apparatus is removed after deflation of the balloon chambers. It has been proposed to use an anaerobic sealant in this process since such sealants have a property, convenient for this application, of being stable on exposure to air but readily and spontaneously curing upon deprivation of oxygen. It has been found however that the anaerobic sealants designed for impregnating rigid articles may not be suitable for sealing leaking gas pipe joints because such sealants produce rigid cured products which are not sufficiently flexible to accommodate the relative movement which underground gas pipes undergo due to gradually applied stresses from soil settling, changes in water table, road vibrations, etc. Thus, an improved anaerobic sealant suitable for sealing leaks in underground gas pipes is desirable.